Symptoms

A couple of the Workspace Tabs have gone away. The Management and Security tabs have disappeared and I am not able to get them back.
 

Diagnoses

The Workspace Permissions start out as a blank slate. If no permission have been specified, everyone has access to each tab. Once a user is added via the Security tab, all other users are locked out until they are added.
 

Resolution

#1. Take a backup of the K2 Database
#2. Run the following SQL Query, this will give all users access to all tabs in Workspace
-TRUNCATE TABLE Workspace.ActionPermission
#3. Restart the K2 Server.
#4. All users now have access to all Workspace tabs.